air tightness test
Jul 22
How to Pass an Air tightness Test
  • July 12, 2022
  • admin

An Air tightness test, also known as the Air Leakage Test, is the measurement of the amount of air that flows through the envelope of a building. The air leakages factor is a challenge that affects various buildings, with the test being a priority these days, something that was not there in the past years.

The Air tightness test detects the leakage of air and the uncontrolled flow of this air that happens through the cracks and cavities within the buildings, which are brought about by damages done to the building, bad weather, or ineffective design construction work. This test is required before allowing occupation in a newly built building.

How To Pass Air Tightness Test for The First Time

Air leakages can be dangerous to occupants of a particular building since they lead to heat loss, making it hard for air to move freely or condense at some points in the building. Failing to participate well in the air tightness testing requirements can be very costly, especially if it’s your first time.

You need to be smart enough and acquire an air tightness strategy to reduce the risk of failing the test. Some challenges come hand in hand with failing the test, with the crucial one taking a long time to complete your building, not forgetting the additional cost and retest fees accompanying this delay.

It would help if you did not spend more than the initial cost of building airtight buildings, provided you can access a good air tightness strategy such as one from BERL.IE that will guide your construction work and deliver good results.

What You Need to Test

Residential buildings that have been newly built require building regulations approved document from the air leakage test. However, in this test, designed ventilation systems are not included. 

The test requires an assessment of the chimneys, extractors, and MVHR units to give its score. There are key factors that you need to put into consideration when carrying out your construction work.

Design Tight

You must come up with an air tightness strategy as early as possible and make sure that it runs throughout the process of the construction stage. During the design stage, which is normally the key stage of setting up the building, you must consider several things.

First, identification of the air tightness barrier is key. Designate the tightness barrier on the heated envelopes on the entire building. After defining these barriers, you can make markings on these barriers using drawings that are relevant to the construction.

Again, build-up materials such as VLC membrane, purged concrete, and wet plasters are the main materials that form the barriers witnessed in the building. You need to be specific with these materials and keenly note them.

Material junctions such as where the slab meets the wall need clear attention. You should provide clear, straightforward details of these junctions, not forgetting information that is accredited and enhanced.

You should ensure you have a detailed list of the construction work concerning all penetrations in the building, which may have the status of the joints on the floor and even the beams. Also, don’t forget to make another one that focuses on all service penetrations, including water, gas, ventilation, and electrics.

Part F of the building regulation policies may interfere with your construction if not properly followed throughout your construction process. You should ensure that your airtight design allows enough ventilation to meet the regulation policy of requirement.

Ensure that the air tightness strategy document defines your design because it is key in avoiding inconveniences in your construction. You should also make sure that the design aligns with the relevant parties that are part of the design and the construction team.

You should make sure you look for an expert in the air tightness sector who will play a key role in ensuring that the strategy used in the construction is followed to the latter throughout the phases of your construction.

Build Tight

All contractors and subcontractors must be aware of the strategy of the tightness and the reason why you should not destroy the air barrier at any point. It is a must for a tightness briefing to be available at the induction site to aid in the flow of the regulations.

 A tightness champion should be at the forefront of regularly checking up on the air tightness levels of the contractors at every phase of construction of a particular building. At these construction stages, it is important to check the following:

Ground floor

 It would help if you formed the continuous air barrier from the damp proof membrane and the damp proof course in the walls. You should make sure you repair any forms of tears or punctures that may present at the membrane.

You should carefully seal the space between the blocks and the perimeter for beam and block floors. You can do this sealing effectively through the use of the grout, a membrane, or a cement wash.

At times, the gaps in the floor beams and joints may penetrate the external walls of the building. You should make sure you seal these gaps effectively to prevent the risk of the outer wall being exposed.

It would be best if you cut the penetrations services to the required minimum size and seal them well enough to prevent leakage. Make sure you seal the penetrations as early as you can immediately after they are exposed to prevent covering up.

Requirements for the Walls

If you are dealing with the traditional block masonry wall, you should ensure you fill all the mortar joints in the brickwork. It is advisable to use a wet plaster to create an airtight seal on the walls.

It would help if you looked keenly through the blockwork to ensure no gap is left around the penetration area. You should ensure that you effectively use the cavity closers to seal the door and window cavities in your building. Before beginning the construction of the internal walls, you should ensure that you are done with sealing the external walls.

Again, if you are using timber and frame for your construction, you should employ a vapor control layer that you will use to provide an effective airtight barrier. Tape all joints and laps in the membrane as you use dry lining to form a barrier between the timber and the masonry walls.

For Joints on the Floor

The joint hangers on the floor should be used where necessary. It would help if you used to make sure you seal the spaces using a flexible sealant that is created whenever the joints penetrate the walls. The point where the walls and roofs or ceiling meet is where the sealants should be applied to ensure a continuous barrier is achieved.

For the Roof and Ceiling

 It would help if you created a continuous air barrier in the spaces between the heated rooms and the unheated lofts. Switches, light fittings, and downlights should be well sealed all over the building.

Seal all penetration services in the loft spaces as you employ air barriers at the boiler cupboards. The loft hatch is usually not taped during the test. However, it is important to seal it airtight.

For Windows and Doors

Use the cavity closers to seal the openings present at the reveals of the wall. Ensure that your doors and windows are fitted with tight seals at the edges. In cases of double doors, you should seal the frames from inside to avoid uncontrolled airflow.


When you want to establish a build tight, you must put in place the right ventilation for the building. As much as the air leakages cause energy waste, their inadequate flow can put you at a condensation risk; therefore, you must balance this air flow adequately.

Leave a Reply